Many things on screen: cheat sheet

left

Turn anticlockwise by this many degrees.

left(90)

Example

forward(60)
left(90)
forward(60)

penup

Lift the pen so moving does not draw.

penup()

Example

forward(40)
penup()
forward(40)
pendown()
forward(40)

What it draws — Pen up for the middle part

for loop

Repeat the indented lines this many times.

for i in range(4):
    pass

Example

for i in range(5):
    forward(15)
    penup()
    forward(10)
    pendown()

every other

i % 2 == 0 is true on every second pass.

for i in range(8):
    if i % 2 == 0:
        pass
    else:
        pass

Example

for i in range(8):
    if i % 2 == 0:
        pencolor("red")
    else:
        pencolor("blue")
    pensize(6)
    forward(30)
    right(45)

Red and blue sides, taking turns

counter step

Use the counter i to make each pass different.

for i in range(20):
    forward(i * 5)
    right(90)

Example

for i in range(30):
    forward(i * 5)
    right(90)

list

Keep many values in order under one name. The first item is place 0.

colours = ["red", "blue", "green"]

for each item

Work through a list, one item at a time.

for c in colours:
    pass

Example

pensize(6)
for c in ["red", "blue", "green"]:
    pencolor(c)
    forward(40)

print

Show text or a value in the output box.

print("Hello")

random number

Pick a random whole number between two values.

import random

n = random.randint(1, 10)

onkey

Run a function every time a key is pressed. Click the picture first so it receives keys.

def go_up():
    forward(20)

onkey(go_up, "Up")
listen()
mainloop()

Example

def go_up():
    forward(20)

go_up()
go_up()
go_up()

After pressing Up three times

str

Turn a number into text, so it can be joined: "Score: " + str(score).

str(score)

new turtle

Make another turtle with its own name. Put the name and a dot in front of a command to give it to that turtle.

star = Turtle()
star.shape("circle")
star.forward(50)

in

True if the item is in the list (or the key is in the dictionary, or the letters are in the text).

if item in bag:
    pass

goto

Jump to a position. (0, 0) is the centre; x goes right, y goes up.

goto(0, 0)

Example

goto(80, 60)

From the centre to (80, 60)

speed

How fast the turtle moves, from 1 (slow) to 10 (fast).

speed(10)

square (loop)

Draw a square by repeating forward and right four times.

for i in range(4):
    forward(100)
    right(90)

running total

Start the total at 0 once, then add to it on every pass.

total = 0
while total < 10:
    total += int(input("Add: "))

if / else

Do one thing or the other, depending on a condition.

if x > 0:
    pass
else:
    pass

Example

for x in [-90, -30, 30, 90]:
    penup()
    goto(x, 0)
    if x > 0:
        dot(30, "red")
    else:
        dot(30, "blue")
hideturtle()

variable

Give a value a name, so you can reuse and change it.

size = 50

Example

length = 120
forward(length)
left(90)
forward(length / 2)

grow value

Change a value every pass: read the old one, store a new one.

size = 5
for i in range(20):
    forward(size)
    right(90)
    size = size + 5

Example

size = 5
for i in range(30):
    forward(size)
    right(90)
    size = size + 5

def (function)

Name a group of steps, then run it by calling its name.

def shape():
    pass

shape()

Example

def zigzag():
    left(45)
    forward(30)
    right(90)
    forward(30)
    left(45)

zigzag()
zigzag()
zigzag()

ontimer

Run a function again after a number of milliseconds. A function can start its own timer.

def tick():
    forward(5)
    ontimer(tick, 50)

tick()
mainloop()

join text

Join pieces of text into one with +. Spaces only appear where they are inside the quotes.

"Hello, " + name

add to (+=)

Add to a variable: total += 5 is short for total = total + 5.

total += 1

dictionary

Values stored under names (keys). One dictionary can hold everything about one thing.

star = {"speed": 5, "points": 1}

dictionary value

The value stored under that key. The key goes in quotes. Assign to it to change it: star["speed"] = 8.

star["speed"]